Effect of Intrathecal Injection of Immune Inhibitor Dexamethasone in the Treatment of Chronic Neuropathic Pain

Objective:To investigate the effect and the likely mechanism of immune inhibitor dexamethasone in the treatment of the chronic neuropathic pain by intrathecal injection and to suggest a new approach to the treatment.Methods:36 SD rats were divided into 3 groups.Group A(n=12,sham operation+saline treatment);Group B(n=12,chronic constrained injury+saline treatment);Group C(n=12,chronic constrained injury + dexamethasone).Sciatic nerve ligature was performed classically in Group B and C to construct CCI model.The sciatic nerve of rats in Group A were exposed only,with no ligation.Dexamethasone was administered through PE-10 tube in Group C in 2,4,6,8,10,12 after operation,while the rats of Group A and B were given equal amount of saline at the same time.Pain threshold was recorded 1,3,7,14 days after operation.The rats were sacrificed at the end of the 2nd week,and the GFAP and the expression of TNF-αin spinal cord were determined by immunohistochemistry.Results:①Behavioral tests of threshold: compared to that of Group A,the threshold of Group B and C decreased after CCI operation(P0.01);compared to that of Group B,the hyperalgesia showed a withdrawal postligation of sciatic verve in group C.②Immunohistochemistry:a.GFAP staining: Spinal astrocytic activity was elevated in rats of Group B and C except of the sham group(P0.05).b.TNF-α expression:TNF-α expression of Group B tended to be weak-postive,but that of Group Ctended to be strong-positive.There was statistical significance,when compared(P0.05).Conclusion:Dexamethasone has obvious therapeutic effect in the treatment of the chronic neuropathic pain.